There is a group of plastic dental filling materials called "composites". These consist of two components, a base and a catalyst which must be mixed together immediately prior to insertion in a cavity in a tooth. Various fillers are incorporated in one or the other of the components to add certain properties to the composite. Materials like powdered quartz or other silicates add resistance to wear and increase translucency. Pigments or opacifiers are added to the composite to enable closer color matches to the natural teeth.
The two components come in varying physical states. They may each be pastes, powder and liquid, and one brand uses a paste for the base and incorporates the catalyst into the sheets of the disposable paper mixing pads.
Practically all the brands supply disposable pads of paper, usually glazed, upon which the portions of base and catalyst are mixed together with a disposable plastic spatula. Except for the one brand described above, where the catalyst is impregnated into the mixing paper, the paper serves only the mechanical purpose of supplying a smooth expendable mixing surface.
The companies supply the composites in various shades which will match the gamut of colors found in natural teeth. Blending may be performed by the dentist among the various colors in order to obtain a better color match. Usually three or four basic shades will be adequate to match the majority of teeth.